1. Field of the Invention
This invention relates to rotary compressors, and in particular to bore contours for the compression cylinder of rotary compressors.
2. Description of the Background Art
In U.S. Pat. No. 3,499,600, of Ralph McGregor, which patent is owned by the assignee hereof, a rotary compressor is disclosed having a single blade construction including a unique configuration for the blade tips and a unique contour for the chamber wall of the compression cylinder. The contour cylinder bore provides an increase in the cross-sectional area of the chamber as compared to a round cylindrical chamber, with the maximum increase occurring at points spaced 90.degree. and 270.degree. from the point where the rotor is most closely juxtaposed to the cylinder wall. More specifically, the cross-sectional area of the chamber adjacent the transfer slot is greater than that of a round cylinder, permitting the discharge region of the compressor to be configured for minimizing re-expansion of compressed gas in the outlet, thereby causing the discharge pressure to more closely approximate the highest pressure within the compression chamber.
A number of other prior art compression chamber configurations have been developed for use in rotary compressors. Illustratively, Amandus C. Roessler shows, in U.S. Pat. No. 986,502, a rotary compressor having a nonsymmetrical bore that is opened up in the throat area. As shown in the drawing, the contour differs from a cylindrical contour in two adjacent quandrants.
In a second U.S. patent of Amandus C. Roessler, No. 2,278,740, a rotary pump is disclosed which again enlarges the cylinder contour in two adjacent quadrants preceding the discharge port.
In U.S. Pat. No. 3,642,390 of Bernard N. Ostberg, a compressor is shown having a symmetrical contour about a line drawn through the contact point and center of the rotor, with the contour being enlarged in the quadrant containing the discharge port and the quadrant containing the suction inlet.
Another compressor is illustrated in U.S. Pat. No. 4,133,617 of Denis A. L. M. Reynaud. The compressor thereof is provided with a cylinder configuration having a noncircular, symmetrical bore contour.
A two-blade compressor having a symmetrical bore contour is disclosed in U.S. Pat. No. 2,347,944 of Elbert Fowler. As shown therein, the bore contour is defined by two opposite concentric arcs of unequal radii which are joined by a noncircular curved portion defined by a specified formula.
In Japanese Utility Model Application No. 3530-1974, another symmetrical cylinder configuration is disclosed, wherein a cycloidal cam function is applied over the first and second quadrants of the bore. The configuration appears to be symmetrical about an axis defined by the rotor contact point and the rotor center.